Palladium (0) olefin complexes bearing purine-based N-heterocyclic carbenes and 1,3,5-triaza-7-phosphaadamantane (PTA): Synthesis, characterization and antiproliferative activity toward human ovarian cancer cell lines

A complete series of new η²-olefin palladium (0) complexes bearing purine-based N-heterocyclic carbenes or PTA (1,3,5-triaza-7-phospaadamantane) as spectator ligands have been synthetized and exhaustively characterized. The first single-crystal X-ray structure of a PTA complex of palladium (0) have been also reported. The most part of these compounds have been tested as antiproliferative agents toward two different human ovarian cancer cell lines A2780 and A2780cis, respectively cisplatin sensitive and resistant. The resulting IC₅₀ values have shown the significant antiproliferative activity of our complexes, often comparable with cisplatin. In some cases, this cytotoxicity is associate with induction of apoptosis. The efficiency of the Pd (0) complexes is heavily influenced by the combination of spectator ligands and coordinating olefin. Finally, two of the most active compounds against cancer cells proved scarcely active on non-tumor fibroblast cells MRC-5.